The present invention relates to friction clutches in general and more specifically to diaphragm type friction clutches.
Diaphragm type friction clutches have found wide acceptance in the automotive industry over the years due to the fact that they require considerably less axial space than other types of friction clutches. The reduced axial length results from the combined use of a flat dished-shaped diaphragm spring for engaging and disengaging the clutch and flat radially disposed resilient straps for providing the necessary drive and axial flexibility to permit the engaging disengaging operation to take place.
One well known friction clutch of this type is shown in U.S. Pat. No. 2,770,341 which issued Nov. 13, 1956 to M. T. Woobrock. In such a clutch, the diaphragm spring is normally supported with respect to the clutch cover by a plurality of fastening means, such as rivets, which are secured to the cover and pass through openings in the diaphragm spring. A fulcrum ring is positioned on opposite sides of the diaphragm spring and supported and positioned by these same rivets so that the spring can be pivotally operated in either direction to control operation of the clutch.
Although this arrangement has proved satisfactory in the past, problems have been encountered in present day applications due to the continually increasing rotational speeds which have produced centrifugal effects sufficient to cause displacement of the diaphragm spring and/or associate fulcrum rings. In a drive system where balance is a finely controlled factor, it can be seen that any such displacement will result in unbalance thereby setting up vibrations and subsequent problems in the vehicle drive line. At initial assembly, the clutch is balanced and the diaphragm spring and fulcrum rings are concentrically located with respect to their support means. However, it has been found that during shipping and also prior to final assembly in a vehicle this balanced condition is sometimes altered due to accidental or careless handling by a worker.
Efforts have recently been directed to providing a more satisfactory support means for the fulcrum rings so that they are prevented from rotating relative to the diaphragm spring or the clutch cover. The former method is shown in British Pat. No. 1,003,406, published Sept. 2, 1965 and the latter in U.S. Pat. No. 3,595,355 which issued July 27, 1971 to P. Maucher. While both designs may be sufficient to restrain the fulcrum rings in their initially assembled and balanced condition, the diaphragm spring in each design is still susceptible to relative movement with respect to the fastening means and thereby the cover since the diaphragm springs are movable with respect to the fastening means due to spacing resulting from the construction of the openings. It will be evident that if the diaphragm spring is not positively constrained in all directions by the fastening means it is subject to radial and/or rotational displacement relative to the cover under the influence of centrifugal force or possibly as a result of accidental dropping or mishandling.
Some very early arrangements have been disclosed which tend to approach a much more satisfactory design and, while somewhat reducing this problem, they have not completely eliminated all possibilities. One design is disclosed in U.S. Pat. No. 2,138,169 which issued on Nov. 29, 1938 to G. Hunt. Another arrangement is shown in U.S. Pat. No. 2,256,708 which issued to H. S. Geyer et al. on Sept. 23, 1941. The latter design illustrates the use of fastening means on the cover for cooperating with openings in the diaphragm spring to prevent rotational displacement of the diaphragm spring with respect to the cover but does not show any means to prevent relative radial displacement therebetween. In this particular patent an annular fulcrum member is provided with a plurality of axial tongues which extend through the openings in the diaphragm spring with the ends of the tongues secured to the cover so as to rigidly secure the fulcrum member to the cover. The width of the tongues is such as to engage the side walls of the openings thereby preventing relative rotation between the cover and diaphragm spring. The former design illustrates, in one embodiment, integral axial lugs on the cover extending through openings in the diaphragm spring and supporting a pair of fulcrum rings. However, neither of these designs show any type of means for positively maintaining the diaphragm spring radially centered with respect to the cover and thereby concentric with the clutch axis.
In clutches of this type, for the reasons pointed out earlier, it is essential that the diaphragm spring be initially located and subsequently maintained in concentric relationship with respect to the clutch axis in order to maintain proper balance and operation throughout the life of such a clutch.
Accordingly, it is an object of the present invention to provide integral support means on a clutch cover which will positively prevent both radial and rotational movement of a diaphragm spring with respect to the clutch cover under all handling and operating conditions.
Another object of this invention is to integral means on a clutch cover which will serve to prevent axial and radial displacement of the fulcrum rings employed in a diaphragm clutch.